Patent GB-303779-A (GB)
Title: Improvements in or relating to electric synchronising apparatus
IPC: H02J3/42
Filed: 1927-10-05
Abstract: 303,779. Reyrolle & Co., Ltd., A., and Warren, T. R. Oct. 5, 1927. Synchronizing dynamo-electric machines; running generators in parallel; regulation, automatic -The speed or frequency of any a.c. dynamoelectric machine, and in particular the frequency of a system supplied from a number of machines in parallel, is controlled by a source of standard frequency and a system of relays operative in accordance with the relation between the machine speed and the standard frequency and controlling the transmission of impulses for the selective operation of means for raising or lowering the speed of the machine or machines. The invention is applicable to the control of a.c. motors when a source of e.m.f. is available the frequency of which depends upon the speed of the motor. The speed or frequency-controlling means may be combined with load sharing arrangements for a group of parallel connected machines so that the load sharing device associated with any machine, the load share of which lies outside predetermined limits, may prevent alteration of the speed of that machine such as would cause its load to deviate further from such limits. In a system comprising a number of sub-stations frequency controlling relays and hand-operated means for controlling the distribution of load among sub-stations may be provided in a control station, these devices acting in conjunction with automatic load-sharing devices in each sub-station to control the speed of the machines'. The speed controlling relays may be used to synchronize an additional machine when required and in a system comprising a number of substations each substation may have a further system of relays for this purpose, a selective remote control arrangement being provided to enable any individual machine to be selected and synchronized under the control of these relays. Fig. 1 shows two a.c. generators A arranged for parallel running and provided with automatic load-sharing arrangements M of the kind described in Specification 296,815. The speeds of these machines are controlled by auxiliary motors K<2>, which may act upon the governors of steam turbines driving them, through speed-lowering and speed-raising contactors K, K<1> energized from lower-speed and raise-speed control bus-bars C<5>, C<6>. When the machine is idle the circuits of the relays K, K' pass through synchronizing plugs B<4>, B<5> and when on load through the load-sharing devices M. The speed control bus-bars C<5>, C<6> are in turn controlled by a system of relays E, G, H, J of which E and G are synchronizing and auxiliary synchronizing relays arranged as described in Specification 294,971 and connected on the one hand to leading and lagging phase busbars C, C' deriving their voltage and frequency from the machine A and on the other hand to a source of standard frequency such as a constant speed a.c. generator D'. While the frequency of the system corresponds with the standard frequency the synchronizing relay E remains energized and the auxiliary synchronizing relay G de-energized. The interrupter relay J is thus energized and no current is supplied to the relay K or K<1>. A change in frequency upwards causes the contacts of the relay G to rise and fall repeatedly; the relay E will be de-energized and remain so. The lower-speed bus-bar C<5> is energized each time the contacts G<4> close but the duration of energization is controlled by the time delay lift interrupter J so that when the frequencies approach equality the impulses become shortened. A change in frequency downwards has a like effect except that the relay E is energized and its contacts maintained lifted by the contacts E<2> and the raise-speed bus-bar C<6> is energized. If the load distribution between the machines shall be unequal the load-sharing devices will have operated to vary the connections of the raise and lower speed contactors on the machines so that the synchronizing relays will only affect the speeds of appropriate machines and the load wilt be correctly distributed at the same time as the frequency is brought to normal. To provide for synchronizing and bringing into circuit an additional machine a synchronizing bus-bar C<2> is connected through a relay F so that upon insertion of a synchronizing plug B<2> a voltage derived from the machine may be automatically connected to the system of frequency control relays in place of the standard frequency source D<1>. The relays E, G then operate with the relay J and the bus-bars C<5>, C<6> to bring the machine up to synchronism whereupon the time delay relay H closes a connection to the circuit-breaker closing bus-bar C<7>. Upon removal of the synchronizing plug the relay F resets and the normal conditions are restored. Fig. 2 shows a system of speed controlling relays X, Y, Z, similar to the relays E, G, J, in a control station for three substations in each of which are a number of machines provided with load-sharing devices m, automatic synchronizing relays e, g, h, j and a known remote controlled device P for selecting any machine for synchronizing. The control station has hand-operated control arrangements N, N', N<2> one connected to each substation through pilot wires. An e.m.f. derived from the system in any substation can be connected through pilot wires to the speed controlling relays X, Y, Z by plugs S whereupon speed controlling impulses depending upon the frequency relation between this e.m.f. and a standard frequency e.m.f. from a machine W<1> will be sent as required through switch U, V and a polarized relay P in the substation to control the speed regulating motors K2 in the substation conjointly with the load-sharing devices. The load on any substation may be raised or lowered by operating one or other of the switches U, V by hand whereby the operation of the relays X, Y, Z is temporarily superseded by current from the bus-bars. T<4>, T<5>.